A nonaqueous battery comprises an active material that can easily react with water (a light metal or its alloy or a material capable of intercalating/deintercalating lithium ion) as a negative electrode. Therefore, the nonaqueous battery is arranged such that there is no water incorporated in the electrolyte, and the battery container is hermetically sealed to prevent water from entering the container. The battery container consists of a can or metal member and an insulating sealing material (also referred to as "gasket"). In order to provide perfect sealing, a sealant is interposed between the can or metal member and the insulating sealing material. As such sealants, there have been proposed various compounds which allegedly can prevent the entry of water and exhibit resistance to an organic solvent, which is contained in the battery as an electricity-generating element. Among these proposed compounds, a pitch (bituminous substance) such as asphalt and coal tar are most widely used. JP-A-56-32671, JP-A-57-194453, JP-A-58-10365, and JP-A-59-859 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") disclose the use of pitch by itself as a sealant. These patents describe that the selection of a particular pitch having proper physical properties or the coating of such a sealant on the surface of both the metal member and the insulating sealing material renders the battery more resistant to liquid leakage at a temperature as high as 60.degree. C. at a relative humidity of 90%. However, their effects leave much to be desired.
Thus, mixtures of pitch with the following compounds have been proposed. One of these proposals is a mixture of pitch with a mineral oil as disclosed in JP-B-61-36344 (the term "JP-B" as used herein means an "examined Japanese patent publication"). This proposal allegedly provides a further improvement in the resistance of the battery to liquid leakage during storage at a temperature as high as e.g., 60.degree. C. for 100 days or in a 60.degree. C.-minus 10.degree. C. heat cycle. JP-A-U-57-194254 (the term "JP-A-U" as used herein means an "unexamined published Japanese utility model application"), JP-A-58-112246, JP-A-59-78443, and JP-A-63-80471 disclose mixing a pitch with a silicone rubber. This approach allegedly provides an improvement in the resistance of the battery to liquid leakage during storage at a temperature as high as e.g., 60.degree. C. for 100 days or in a 60.degree. C.-minus 10.degree. C. heat cycle. Further, a method which comprises mixing a pitch with a thermoplastic or thermosetting resin is proposed in JP-A-59-91660, and JP-A-63-202845. This approach allegedly provides an improvement in the resistance of the battery to liquid leakage during storage at a temperature as high as e.g., 60.degree. C. or 70.degree. C. for 100 days or in a 60.degree. C.-minus 10.degree. C. heat cycle by mixing a pitch with vinyl acetate or atactic polypropylene as a resin. JP-B-63-1706 discloses that the use of a cationic aqueous dispersion obtained by dispersion-suspending either a pitch (asphalt) or a rubber latex (e.g., styrene-butadiene rubber, butadiene rubber, chloroprene rubber, ethylenepropylene rubber) or a mixture thereof in water with a cationic surface active agent as a sealant allegedly provides an improvement in the resistance of the battery to liquid leakage during the storage at a temperature as high as 45.degree. C. at a relative humidity of 90% for 1 to 12 months. These approaches do provide an improvement in the resistance of the battery to liquid leakage during storage at elevated temperature. However, even these improved approaches leave much to be desired in the following respects.
The sealing of a nonaqueous battery can be accomplished by pressing a negative electrode can or positive electrode can against an insulating sealing material made of a synthetic resin via a sealant as shown by the reference numerals 12, 13, 14 and 15 in FIG. 2. The strength by which the negative or positive can is pressed against the sealing material is sealing strength. The sealing strength is affected by the shape of the sealing mold and the molding size of the insulating synthetic resin sealing material or metal member. In particular, the sealing mold is gradually worn away as the sealing process is repeatedly conducted. As a result, the sealing strength is gradually reduced. Therefore, nonaqueous batteries prepared according to the aforementioned proposed methods leave much to be desired in their resistance to liquid leakage when the sealing strength is reduced.